I like how easy it was to set up my build pipeline using Jenkins as our CI/CD tool - we used CircleCI before but they were very slow compared to other services out there (which have since been acquired). The interface could be improved though; some things are hard or even impossible without plugins which would require an extra setup step in order get working correctly! Also not being able to link multiple branches together into one job can sometimes cause problems when trying to figure what's going wrong if something fails after several builds pass successfully. We use this service because their UI makes managing jobs so much easier than having them written manually by us developers ourselves.